Permanent magnet and method of making the same



July 3, 1928.

J. H. WHITE PERMANENT MAGNET AND METHOD OF MAKING THE SAME Filed May 8, 1925 Patented July 3, 1928.

UNITED STATES PATENT OFFICE.-

JOHN H. WHITE, CRANFORD, NEW JERSEY, ASSIGNOR, BY MESNE ASSIGNMENTS, TO WESTERN ELECTRIC COMPANY, INCORPORATED, A CORPORATION OF NEW YORK.

PERMANENT MAGNET AND METHOD OF MAKING THE SAME.

Application filed. May 8,

This invention relates to permanent magnets and particularly to telephone receiver permanent magnets.

An object of this invention is to provide a cheap method of making permanent magnets by the chilled casting process whereby the castings are sufficiently hard to be immediately given their permanent magnetization.

Heretofore permanent magnets have been fabricated from' wrought bars of carbon steels often containing tungsten or other added metals, and then hardened by reheat-- ing and quenching. This method of manufacture is difiicult and expensive because of the liability of cracking during the forging and quenching processes.

By this invention the aforementioned forging, reheating and quenching processes are dispensed with by directly casting the molten alloy into chilled molds of the form desired for the finished magnet, thus making a chilled casting having all the qualities desired in-permanent magnets for telephone receivers.

The advantages of this invention may be realized in a telephone receiver of the watch case type and accordingly the practice of this invention in a receiver of that type is described specifically by way of example in the following specification.

The principle upon which this invention is based can be better understood after a description of the type of instrument to which it is applicable. Reference is made, therefore, to the accompanying drawing in \vhichFig. l is a plan View ofa watch case type of receiver, utilizing the magnet of this invention, with the ear cap and diaphragm removed, Fig. 2 is a plan view of the magnet, and Fig. 3 is an edge view of the same.

Referring particularly to Fig. 1, numeral 1 designates the receiver case which forms a housing for the permanent magnet 2, the poles of which are secured to the pole pieces 3 by means of the nuts 4 and studs 5 which are. rigidly attached to the face of housing 1. The pole pieces 3, which may be cast integral with thev magnet if desired. have vertical projections 6 upon which the receiver 1925. Serial No. 28,873.

coils 7 are wound, terminating in the contact 8 to which are attached the two telephone cord leads, which are suspended by a strain relieving cord from an eye 9 secured to the outside of housing 1.

In practicing this invention an iron mold is provided having the shape desired, which, for the purposes of this invention, may be. that shown in Figs. 2 and 3. Inasmuch as magnet steel is very hard and resists any drilling, soft iron slugs, designated by numeral 10 in Fig. 2, are inserted in the mold in the manner of a core so that the magnet may be readily drilled at 11 for the studs 5 shown in Fig. 1. The molten magnet steel, which ma be for example of the type disclosed in atent 1,338,133 of April 27, 1920, is poured into the cold iron mold and results in a chilled casting sutliciently hard for permanent magnets without the necessity of subsequent heat treatment. The sprue and riser gates are broken oil and the casting at these points ground ofi' flush, the holes 11 drilled through the soft iron inserted cores 10 and the magnet is ready for the magnetizing process.

An obvious advantage of the process disclosed by this invention is that magnets may be made into the various special forms and shapes most desirable from the magnetic oint of view, which, because of the inherent rittleness of magnet steel, are ditlicult and expensive to make under the existing processes of manufacture.

WVhile this specification describes a specitic process utilizing various magnet steels, it is to be understood that the composition of such steels is not limited in any manner but may include any such combinations of elements as will increase the magnetism of steel, and fin-t-hern'iore, changes may be made in the methods and forms of manufacture without departing from the spirit of this invention within the scope of the appended claims. 7

'hat is claimed is:

l. A chilled east magnet steel permanentmagnet provided with soft metal inserts.

2. The method of making permanent magnets consisting in pouring molten magnet steel into a chilled mold and thereafter magnetizing the casting.

3. The method of forming telephone receiver magnets consisting in casting magnet steel in a chilled mold to produce a hard core of suitable shape without further heat treatment, and thereafter ma'gnetiz ing the casting.

4. The method of forming permanent magnets consisting in placing machinable inserts in a chilled mold and pouring molten magnet steel into the mold and around the inserts and thereafter magnetizing the castmg.

In witness whereof, I hereunto subscribe my name this 1 day of May, A. D. 1925.

JOHN H. WHITE 

